Abstract

The night of 14 December 2010 radar images of the Spanish Weather Agency recorded a large rain
band that moved o
ff
shore at the Northeast coast of the Iberian Peninsula. MM5 mesoscale model is used to
study the atmospheric dynamics during that day. A Nocturnal Low Level Jet (NLLJ) generated by an inertial
oscillation that brings cold air to the coast from inland has been simulated in the area. This cold air interacts
with a warmer air mass some kilometers o
ff
shore. According to the MM5 mesoscale model simulation, the cold
air enhances upward movements of the warm air producing condensation. Additionally, there is a return flow to
the coastline at 600–900 m high. This warm air mass interacts again with the cold air moving downslope, also
producing condensation inland. The simulation for the night before this episode shows large drainage winds
with a NLLJ profile, but no condensation areas. The night after the 14th the simulation also shows drainage
winds but without a NLLJ profile. However, an o
ff
shore convergence area was produced with a returned flow,
but no condensation inland occurred. This fact is in agreement with radar observations which reported no
precipitation for these two days. Consequently, NLLJ in combination with a synoptic wind over the sea could
enhance condensation and eventually precipitation rates in the Mediterranean Iberian coast.

CitacióMazon, J.; Pino, D. The role of nocturnal Low-Level-Jet in nocturnal convection and rainfalls in the west Mediterranean coast: the episode of 14 December 2010 in northeast of Iberian Peninsula. "Advances in science and research (ASR)", 19 Març 2012, vol. 8, p. 27-31.